1. The Heart A muscular double pump
Pulmonary circuit – takes blood to and from the lungs
Systemic circuit – vessels transport blood to and from body tissues
Atria – receive blood from the pulmonary and systemic circuits
Ventricles – the pumping chambers of the heart

2. The Pulmonary and Systemic Circuits
Figure 18.1

3. Location and Orientation within the Thorax
Figure 18.2

4. Structure of the Heart – Coverings
Figure 18.3

5. Structure of the Heart – Layers of the Heart Wall
Epicardium – visceral layer of the serous pericardium
Myocardium – consists of cardiac muscle
Muscle arranged in circular and spiral patterns
Endocardium – endothelium resting on a layer of connective tissue
Lines the internal walls of the heart

6. Heart Chambers Internal divisions External markings
Atria and ventricles
Interventricular and interatrial septa
External markings
Coronary sulcus
Anterior and posterior interventricular sulcus

7. Heart Chambers
Figure 18.5b

8. Heart Chambers
Figure 18.5e

9. Inferior View of the Heart
Figure 18.5d

10. Pathway of Blood Through the Heart
Begin oxygen-poor blood in the superior and inferior venae cavae
Go through pulmonary and systemic circuits

11. Blood Flow Through the Heart
Figure 18.6

12. Pathway of Blood Through the Heart
Figure 18.6b

13. Systole and diastole also refer to:
Heartbeat
70–80 beats/minute at rest
Systole – contraction
Diastole – expansion
Systole and diastole also refer to:
Stage of heartbeat when ventricles contract and expand

14. Structure of Heart Wall
Walls differ in thickness
Atria – thin walls
Ventricles – thick walls

15. Structure of Heart Wall
Left ventricle – three times thicker than right
Exerts more pumping force
Flattens right ventricle into a crescent shape
Figure 18.7

16. Heart Valves – Valve Structure
Figure 18.8a

17. Function of the Atrioventricular Valves
Figure 18.9a

18. Function of the Atrioventricular Valves
Figure 18.9b

19. Function of the Semilunar Valves
Figure 18.10a, b

20. Heart Sounds
“Lub-dup” – sound of valves closing
First sound “lub” – the AV valves closing
Second sound “dup” – the semilunar valves closing

21. Heart Sounds
Figure 18.8a

22. Each valve sound – best heard near a different heart corner
Heart Sounds
Each valve sound – best heard near a different heart corner
Pulmonary valve – superior left corner
Aortic valve – superior right corner
Mitral (bicuspid) valve– at the apex
Tricuspid valve – inferior right corner

23. Heart Sounds
Figure 18.11

24. Surrounds all four valves Functions
Fibrous Skeleton
Surrounds all four valves
Composed of dense connective tissue
Functions
Anchors valve cusps
Prevents overdilation of valve openings
Main point of insertion for cardiac muscle
Blocks direct spread of electrical impulses

25. Cardiac muscle tissue has intrinsic ability to:
Conducting System
Cardiac muscle tissue has intrinsic ability to:
Generate and conduct impulses
Signal these cells to contract rhythmically
Conducting system
A series of specialized cardiac muscle cells
Sinoatrial (SA) node sets the inherent rate of contraction

26. Microscopic Anatomy of Heart Muscle

27. Cardiac Muscle Contraction
Heart muscle:
Is stimulated by nerves and is self-excitable (automaticity)
Contracts as a unit
Has a long (250 ms) absolute refractory period
Cardiac muscle contraction is similar to skeletal muscle contraction

28. Heart Physiology: Intrinsic Conduction System
Autorhythmic cells:
Initiate action potentials
Have unstable resting potentials called pacemaker potentials

29. Heart Physiology: Sequence of Excitation

30. Heart Physiology: Sequence of Excitation
Sinoatrial (SA) node generates impulses about 75 times/minute
Atrioventricular (AV) node delays the impulse approximately 0.1 second
Impulse passes from atria to ventricles via the atrioventricular bundle (bundle of His)

31. Heart Physiology: Sequence of Excitation
AV bundle splits into two pathways in the interventricular septum (bundle branches)
Bundle branches carry the impulse toward the apex of the heart
Purkinje fibers carry the impulse to the heart apex and ventricular walls

32. Heart Excitation

33. Heart rate is altered by external controls
Innervation
Heart rate is altered by external controls
Nerves to the heart include:
Visceral sensory fibers
Parasympathetic branches of the vagus nerve
Sympathetic fibers – from cervical and upper thoracic chain ganglia
Figure 18.13

34. Blood Supply to the Heart
Functional blood supply
Coronary arteries
Arise from the aorta
Located in the coronary sulcus
Main branches
Left and right coronary arteries

35. Blood Supply to the Heart
Figure 18.14

36. Coronary artery disease
Disorders of the Heart
Coronary artery disease
Atherosclerosis – fatty deposits
Angina pectoris – chest pain
Myocardial infarction – blocked coronary artery
Silent ischemia – no pain or warning

37. Congestive heart failure – heart enlarges Cor pulmonale
Disorders of the Heart
Heart failure
Progressive weakening of the heart
Cannot meet the body’s demands for oxygenated blood
Congestive heart failure – heart enlarges
Pumping efficiency declines
Cor pulmonale
Enlargement and potential failure of the right ventricle

38. Disorders of Conduction
Ventricular fibrillation
Rapid, random firing of electrical impulses in the ventricles
Atrial fibrillation
Multiple waves of impulses randomly signal the AV node
Signals ventricles to contract quickly and irregularly

39. The Heart Throughout Life
Blood vessels
Begin as condensations of mesodermal mesenchyme
Embryonic heart
Pair of tubes fuse at day 21
Heart starts pumping at day 22
Bulges develop along heart tube

40. Congenital Heart Defects
Figure 18.17a, b

41. Congenital Heart Defects
Figure 18.17c, d

42. Congenital Heart Defects
Figure 18.17e, f

43. The Heart in Adulthood and Old Age
Age-related changes
Hardening and thickening of valve cusps
Decline in cardiac reserve
Sympathetic control over heart is less efficient
Less severe in the physically active
Fibrosis of cardiac muscle tissue
Lowers the amount of blood the heart can pump